The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The European patent EP 0338 806 A1 (Holman and Marchall) teaches a syringe comprising a body, a dose-setting device in the form of a rotary cap or ring mounted on the body and capable of being moved to a selected set position where a latch is arranged to retain the setting device in that set position, the movement of the setting device being accompanied by straining of a spring, which, when the latch is released, provides the force for expelling the set dose, characterised by means arranged to release the latch, which causes the return of the setting device to an original position to drive a plunger through a one-way clutch to expel the set dose; and by a quick pitch screw thread arrangement capable of transforming rotation of the setting device into linear movement of the plunger.
The indication mechanism in this syringe is designed in such way, that the displacement of the plunger is obtained by using the energy gathered in a helical spring, which is twisted, during the preliminary setting of the dose to be injected, by means of the rotation of a rotary cap or ring, which is rotateably mounted on sleeve having a degree scale at the right end of the syringe “pen” body. The rotary cap or ring has an inspection window showing an angle of the rotation of the said rotary cap or ring to be read from the scale.
The main disadvantage of the mechanism consists in that the scale comprises at the most only one complete rotation, which does not ensure its adequate precision.
Also Polish patent application P 341 395 teaches a syringe for distribution of set doses of a medicine from a cartridge containing the amount of the medicine sufficient to prepare several treatment doses, comprising a housing, a piston rod having noncircular cross-section and an external screw thread, a piston rod drive arrangement comprising two elements, i.e. piston rod leaders and a nut with an internal screw thread corresponding to the piston rod external screw thread, as well as a dose-setting mechanism comprising non-self-blocking screw thread connection, along which an injection push-button is unscrewed from the nearer housing end, causing rotation of the dose-setting element. This syringe is characterized in that between the nut and the piston rod leaders there is unidirectional coupling enabling the rotation of both these parts in one direction but not in the opposite direction, wherein the allowed rotation is the only one, by means of which the piston rod is moved in the circumferential direction in the syringe. The coupling is designed in such way that the initial resistance, sufficient to resist the torque exerted on the coupling by setting a dose, has to be overcome to allow rotation.
The indication mechanism in this syringe is designed in such way, that a convex spiral rib, constituting a quick thread, is formed on the internal wall of the second part of the housing. On the external wall of the dosing barrel having a scale there are spiral grooves defining external thread matching the internal thread of the housing. The pitch of the threads exceeds the friction angle form the materials of the threaded parts, therefore the coupling is not self-blocking and causes one part of the coupling to rotate, when another part is displaced linearly. Numbers indicating the set doses are printed on the external wall of the dosing barrel, and indicated in a window situated in a side wall of the housing.
The European patent EP 1 351 732 A1 (ENGGAARD CHRISTIAN) teaches a dose setting device for use in combination with a fluid-filled reservoir, the dose setting device being adapted for repetitive injection of individually set doses of fluid from the reservoir, the dose setting device comprising: a housing, a drive member adapted to expel a dose of medicine from the reservoir, a spring means, a dose setting assembly mounted in the housing and connected to the spring means, the dose setting assembly comprising a dose setting member being moveable in a first direction to a selected set position against the bias of the spring means, wherein movement of the dose setting member is accompanied by straining of the spring, and wherein the dose setting member is moveable in a second direction to selectively adjust the set dose, a latch means associated with the housing to retain the apparatus in the set position against the bias of the spring means, and the latch means being releasable to cause the drive member to expel the set dose from the syringe, the force for expelling the set dose being provided by the spring means.
The dose setting member comprises a foremost end wall and a rearwardly arranged skirt portion. The end wall has an opening with an internal thread, the end wall thereby serving as a second nut member through which the plunger is arranged. The thread corresponds to the internal thread thus allowing non-locking rotation of the plunger. The end wall further comprises a rearwardly facing coupling surface to be described below. The skirt portion of the dose setting member comprises longitudinal grooves on its inner surface engaging corresponding longitudinal tongue members on the outer surface of the skirt portion of the knob, whereby the two skirt members are allowed to slide axially but not to rotate relative to each other. Indeed, any suitable configuration could be used to provide this functional relation between the two skirt members. Numbers (not shown) are printed along a helical line on the external surface of the skirt which can be inspected through a window in the housing of the device, the window allowing only a portion, preferably only one, of the numbers on the sleeve to be inspected.
The Polish patent application P 375 372 discloses an automatic applicator particularly for insulin, more particularly for multiple injection application of set doses of a medicine from an exchangeable container, comprising a body housing connected to a housing of an exchangeable container with a medicine, particularly insulin, expelled by a piston connected to a plunger and displaced linearly by means of a leading and blocking driving unit driven via a double clutch unit by a tensioning spring situated in the body housing, tensioned by a rotary hand-dose-setting ring also via a double clutch unit, wherein a leading and blocking driving unit is activated by a trigger unit and a displaceable indicating cylinder is situated on the tensioning spring holder. According to the invention the said automatic applicator is characterized in that the double clutch unit comprises a clutch plate coupled co-axially with a body of the ratchet plate and coupled with pawls having catches meshed disengagingly with a gear ring of a driving nut.
The dose setting mechanism comprises the displaceable indicating cylinder, situated on the tensioning spring holder, is mounted slidingly, coaxially, in the tensioning spring holder groove and has a helical groove on its external surface mated with the internal screw thread of the body housing. Such construction provides for the dosage scale, displaced suitably at the dose-setting, to be well visible through a dose-setting inspection window. Besides, the displaceable indicating cylinder comprises the dose-setting end indicator in the form of a red dot, collaborating with the dose-setting end indicator window opening, provided with the dose-setting end indicator window. The currently set dose can be seen on the displaceable indicating cylinder with the scale through the dose-setting inspection window opening. The cylinder is scaled by every unit and the turning of the rotary hand-dose-setting ring is accompanied by a characteristic clicking at every unit, corresponding to 0.01 ml of insulin. The dose-setting can be realized up to a single unit, wherein the scale visible through the dose-setting inspection window, stops at any value or between the given dose values, as indicated by the arrow of the dose indicator on the housing.
The European patent application EP 1 819 382 A1 (MOLLER CLAUS SCHMIDT and MARKUSSEN TOM HEDE) teaches an injection device a housing with an inner surface provided with threads, a dose setting member adapted to set a dose to be ejected from the injection device, a torsion spring operatively connected to the dose setting member, such that energy is accumulated in the torsion spring upon rotation of the dose setting member, having a rotatably mounted display member threadedly engaged with the threads of the housing and operatively connected with the dose setting member and adapted to display the dose to be ejected from the injection device in accordance with a setting of the dose setting member, the rotateably mounted display member being rotatable over an angle corresponding to at least one revolution of the display member.
The dose setting mechanism of this device comprises the inner surface of housing of the injection device provided with threads. These threads are adapted to engage and co-operate with outer threads of a dose indicator barrel. The dose indicator barrel engages with sliding track of the dose setting member in such a way that the dose indicator barrel is able to slide in said sliding track in an axial direction of the injection device. When the dose setting member is rotated in order to set a dose, the dose indicator barrel rotates with the dose setting member causing the dose indicator barrel to be axially displaced relative to the housing. A window is provided in the housing of the injection device. Through this window, the user of the injection device may view the actual dose setting level from numerals (not shown) provided on an exterior surface of the dose indicator barrel. The numerals are arranged along a helical path.
The main disadvantage of the known devices is lack of the provision of application of the precisely controlled and set dose of a medicine. Earlier designs (e.g. acc. To EP 0 338 806) comprise a scale situated only on one circumference and allow only the placement of the small size prints of indication numerals. Also later, above discussed, designs having a spiral scale on the indication barrel do not fulfill their tasks adequately. Due to the large friction during the displacement along the thread of the housing wall, the precision setting of a dose is difficult. Also, due to the thread crisscrossing the external wall of the indication barrel, the placement on it of the adequately big size prints of indication numerals is not possible.